Compact ultrasonic transducer and ultrasonic surgical instrument including the same

ABSTRACT

A compact ultrasonic transducer for an ultrasonic surgical instrument includes a proximal casing defining a hollow interior and a piezoelectric rod array including a plurality of piezoelectric rods radially spaced-apart from one another and arranged in a longitudinally-oriented direction. The piezoelectric rod array is disposed within the hollow interior. The compact ultrasonic transducer further includes a distal horn including a distal connector configured to engage a waveguide. The distal horn is configured to engage the proximal casing to enclose the piezoelectric rod array within the hollow interior. An ultrasonic surgical instrument including the compact ultrasonic transducer is also provided.

BACKGROUND Technical Field

The present disclosure relates to ultrasonic surgical instruments and,more specifically, to a compact ultrasonic transducer and ultrasonicsurgical instrument including the same.

Background of Related Art

Ultrasonic surgical instruments utilize ultrasonic energy, i.e.,ultrasonic vibrations, to treat tissue. More specifically, ultrasonicsurgical instruments utilize mechanical vibration energy transmitted atultrasonic frequencies to coagulate, cauterize, fuse, seal, cut,desiccate, and/or fulgurate tissue to effect hemostasis.

Ultrasonic surgical instruments typically employ a transducer coupled toa handle of the ultrasonic surgical instrument and configured to produceultrasonic energy for transmission along a waveguide to an end effectorof the ultrasonic surgical instrument that is designed to treat tissuewith the ultrasonic energy. The transducer may be driven by anultrasonic generator that is on-board, e.g., on or within the handle ofthe ultrasonic surgical instrument, or remotely disposed, e.g., as aset-top box connected to the ultrasonic surgical instrument via asurgical cable. The end effector of the ultrasonic surgical instrumentmay include a blade that receives the ultrasonic energy from thewaveguide for application to tissue and a jaw member configured to clamptissue between the blade and the jaw member to facilitate treatmentthereof.

SUMMARY

As used herein, the term “distal” refers to the portion that is beingdescribed which is further from a user, while the term “proximal” refersto the portion that is being described which is closer to a user.Further, to the extent consistent any or all of the aspects detailedherein may be used in conjunction with any or all of the other aspectsdetailed herein.

In accordance with aspects of the present disclosure, a compactultrasonic transducer for an ultrasonic surgical instrument is providedincluding a proximal casing defining a hollow interior, a piezoelectricrod array including a plurality of piezoelectric rods radiallyspaced-apart from one another, arranged in a longitudinally-orienteddirection, and disposed within the hollow interior, and a distal hornincluding a distal connector configured to engage a waveguide. Thedistal horn is configured to engage the proximal casing to enclose thepiezoelectric rod array within the hollow interior.

In an aspect of the present disclosure, the compact ultrasonictransducer further includes a seal disposed between the proximal casingand the distal horn and configured to engage the proximal casing and thedistal horn with one another.

In another aspect of the present disclosure, the seal is configured tosealingly engage the proximal casing and the distal horn with oneanother such that the hollow interior is sealed closed.

In still another aspect of the present disclosure, the proximal casingand the distal horn are at least partially formed of anelectrically-conductive material and the seal is at least partiallyformed from an insulative material to electrically isolate the proximalcasing and the distal horn from one another. In such aspects, one of theproximal casing or the distal horn may be configured to communicateelectrical energy at a first potential to the piezoelectric rod arrayand the other of the proximal casing or the distal horn may beconfigured to communicate electrical energy at a second potential to thepiezoelectric rod array to energize the piezoelectric rod array.

In yet another aspect of the present disclosure, the piezoelectric rodarray defines a radially-symmetric configuration relative to alongitudinal axis defined through the compact ultrasonic transducer.

In still yet another aspect of the present disclosure, the plurality ofpiezoelectric rods is maintained in compression between a proximalsurface of the proximal casing and a distal surface of the distal horn.

In another aspect of the present disclosure, a distance between a centerof mass of the piezoelectric rod array and the distal connector of thedistal horn is one-quarter of a wavelength. Alternatively, a distancebetween a center of mass of the piezoelectric rod array and the distalconnector of the distal horn may be another multiple of one-quarter of awavelength.

In yet another aspect of the present disclosure, an internal cartridgeis disposed within the hollow interior and configured to retain theplurality of piezoelectric rods therein.

An ultrasonic surgical instrument provided in accordance with aspects ofthe present disclosure includes a housing, a waveguide extendingdistally from the housing, an ultrasonic blade disposed at a distal endof the waveguide, and a compact ultrasonic transducer supported by thehousing and coupled to the waveguide such that ultrasonic energyproduced by the compact ultrasonic transducer is transmitted along thewaveguide to the ultrasonic blade for treating tissue therewith. Thecompact ultrasonic transducer includes a proximal casing defining ahollow interior, a piezoelectric rod array including a plurality ofpiezoelectric rods radially spaced-apart from one another and arrangedin a longitudinally-oriented direction in the hollow interior, and adistal horn configured to engage the proximal casing to enclose thepiezoelectric rod array within the hollow interior.

In an aspect of the present disclosure, the compact ultrasonictransducer further includes a seal disposed between the proximal casingand the distal horn and configured to engage the proximal casing and thedistal horn with one another.

In another aspect of the present disclosure, the seal is configured tosealingly engage the proximal casing and the distal horn with oneanother such that the hollow interior is sealed closed.

In still another aspect of the present disclosure, the proximal casingand the distal horn are at least partially formed of anelectrically-conductive material and the seal is at least partiallyformed from an insulative material to electrically isolate the proximalcasing and the distal horn from one another. In such aspects, first andsecond contacts may be disposed within the housing in electrical contactwith the distal horn and the proximal casing, respectively, andconfigured to communicate electrical energy at first and secondpotentials to the piezoelectric rod array via the distal horn and theproximal casing, respectively, to energize the piezoelectric rod array.

In yet another aspect of the present disclosure, the compact ultrasonictransducer is rotatable relative to the housing and the first and secondcontacts and the first and second contacts maintain electrical contactwith the distal horn and the proximal casing, respectively, regardlessof a rotational orientation of the compact ultrasonic transducerrelative thereto.

In still another aspect of the present disclosure, the proximal casingincludes an annular flange extending radially outwardly therefrom. Insuch aspects, the housing includes a support configured to receive theannular flange to rotatably support the compact ultrasonic transducer atleast partially within the housing.

In another aspect of the present disclosure, the distal horn includes adistal connector configured to engage the waveguide and a distancebetween a center of mass of the piezoelectric rod array and the distalconnector is one-quarter of a wavelength.

In another aspect of the present disclosure, the ultrasonic surgicalinstrument further includes a clamp arm movable relative to theultrasonic blade from an open position to a clamping position forclamping tissue therebetween.

In still another aspect of the present disclosure, the ultrasonicsurgical instrument further includes a movable handle associated withthe housing and operably coupled to the clamp arm such that actuation ofthe movable handle moves the clamp arm from the open position to theclamping position.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present disclosure willbecome more apparent in view of the following detailed description whentaken in conjunction with the accompanying drawings wherein likereference numerals identify similar or identical elements and:

FIG. 1 is a perspective view of an ultrasonic surgical instrumentprovided in accordance with the present disclosure, wherein the distalend thereof is enlarged to better illustrate the components and featuresthereof;

FIG. 2 is a side view of a proximal portion of the ultrasonic surgicalinstrument of FIG. 1 with components removed and wherein a portion ofthe housing of the ultrasonic surgical instrument is removed toillustrate the internal components therein including a compactultrasonic transducer in accordance with the present disclosure;

FIG. 3 is a side, perspective view of the compact ultrasonic transducerof FIG. 2 including electrical contacts coupled thereto;

FIG. 4 is a rear, perspective view of the compact ultrasonic transducerof FIG. 2 with a portion removed to illustrate the internal componentsof the compact ultrasonic transducer;

FIG. 5 is an exploded, side, perspective view of the compact ultrasonictransducer of FIG. 2; and

FIG. 6 is a perspective, partial cross-sectional view of the compactultrasonic transducer of FIG. 2 including an interior cartridgeretaining the piezoelectric rods therein.

DETAILED DESCRIPTION

The present disclosure provides a compact ultrasonic transducer andultrasonic surgical instrument including the same, although it isunderstood that the compact ultrasonic transducer of the presentdisclosure is equally applicable for use with other suitable surgicalinstruments.

Referring to FIGS. 1 and 2, an ultrasonic surgical instrument configuredfor use in accordance with the aspects and features of the presentdisclosure is shown generally identified by reference numeral 10.Ultrasonic surgical instrument 10 includes a housing 20, a movablehandle 40 operably coupled to housing 20, a shaft 50 extending distallyfrom housing 20, a rotation knob 60 supported on housing 20 andconfigured for rotating shaft 50 relative to housing 20, and a compactultrasonic transducer 80 (FIG. 2) in accordance with the presentdisclosure supported within housing 20. Ultrasonic surgical instrument10 further includes an end effector assembly 100 disposed at a distalend of shaft 50, a waveguide 120 (FIG. 2) extending through housing 20and shaft 50 and operably coupling ultrasonic transducer 80 to endeffector assembly 100, a drive assembly 140 (FIG. 2) operably coupledbetween movable handle 40 and end effector assembly 100, and anactivation assembly 160 operably coupled to housing 20 for selectivelysupplying energy to compact ultrasonic transducer 80 to drive compactultrasonic transducer 80. Ultrasonic surgical instrument 10 additionallyincludes a cable 200 configured to connect to a generator (not shown) orother power source for driving compact ultrasonic transducer 80.

Housing 20 defines a longitudinally-extending barrel portion 22 and afixed handle portion 26 extending downwardly from barrel portion 22 ingenerally perpendicular orientation relative thereto. Barrel portion 22of housing 20 defines a support 23 configured to rotatably supportcompact ultrasonic transducer 80 at least partially within housing 20.In embodiments, compact ultrasonic transducer 80 is removable fromhousing 20. Compact ultrasonic transducer 80 is described in detailbelow. Barrel portion 22 further defines a distal opening 25 throughwhich shaft 50, the drive sleeve 146 of drive assembly 140, andwaveguide 120 extend in substantially coaxial arrangement. Fixed handleportion 26 of housing 20 is positioned adjacent movable handle 40 toenable a user to grasp fixed handle portion 26 of housing 20 andmanipulate movable handle 40 with a single hand.

Movable handle 40 includes a grasping portion 42 configured tofacilitate grasping and manipulation by a user. Movable handle 40further includes a flange portion 44 extending into barrel portion 22 ofhousing 20. Flange portion 44 is pivotably coupled to housing 20 via apivot pin 46 and defines a bifurcated configuration including first andsecond spaced-apart flange arms 48 (only one flange arm 48 isillustrated in FIG. 2 as it obscures the other flange arm 48) operablycouple to mandrel 142 of drive assembly 140 such that pivoting ofmovable handle 40 relative to housing 20 about pivot pin 46 from aspaced-apart position towards an approximated position translates drivesleeve 146 of drive assembly 140 relative to end effector assembly 100to pivot clamp arm 102 of end effector assembly 100 relative to blade124 of end effector assembly 100 between an open position and a clampingposition for clamping tissue therebetween.

With continued reference to FIGS. 1 and 2, shaft 50 is rotatablysupported by housing 20 and extends distally through distal opening 25of barrel portion 22 of housing 20. Shaft 50 includes end effectorassembly 100 disposed at a distal end thereof. Shaft 50 is disposedabout drive sleeve 146 of drive assembly 140, although it is alsocontemplated that this configuration be reversed, e.g., wherein drivesleeve 146 is disposed about shaft 50. Shaft 50 is longitudinally fixedrelative to housing 20 but is rotatable relative thereto in response torotation of rotation knob 60 relative to housing 20 via couplingtherebetween. Rotation knob 60 is also coupled to drive sleeve 146 andwaveguide 120 such that rotation of rotation knob 60 likewise rotatesdrive assembly 140, waveguide 120, and compact ultrasonic transducer 80relative to housing 20 in response to rotation of rotation knob 60relative to housing 20.

End effector assembly 100 includes clamp arm 102, blade 124 of waveguide120, a pair of clevis members 112 (only one clevis member 112 isillustrated in FIG. 1 with the other being obstructed), and a drive link116. Clamp arm 102 includes a frame 104 and a tissue pad 108 engagedwith frame 104. Frame 104 of clamp arm 102 is pivotably coupled to adistal end portion of shaft 50 by way of clevis members 112. Drive link116 is coupled between frame 104 of clamp arm 102 and a distal endportion of drive sleeve 146 (FIG. 2) such that translation of drivesleeve 146 translates drive link 116 to thereby pivot clamp arm 102between the open and clamping positions.

Waveguide 120 defines a body 122, a blade 124 extending from the distalend of body 122, and a proximal connector 126 extending from theproximal end of body 122. Blade 124 extends distally from drive sleeve146 of drive assembly 140 and shaft 50 and, as noted above, forms partof end effector assembly 100 in that blade 124 is positioned to opposeclamp arm 102 such that pivoting of clamp arm 102 from the open positionto the clamping position enables clamping of tissue between clamp arm102 and blade 124. Blade 124 may define a linear configuration as shown,or may define a curved configuration. Proximal connector 126 ofwaveguide 120 is configured to enable engagement of waveguide 120 withcompact ultrasonic transducer assembly 80, e.g., via a threadedengagement, such that mechanical motion produced by compact ultrasonictransducer assembly 80 is capable of being transmitted along waveguide120 to blade 124 for treating tissue clamped between blade 124 and clamparm 102 or positioned adjacent blade 124.

Drive assembly 140 includes mandrel 142 operably disposed about drivesleeve 146. Mandrel 142 is configured to receive flange portion 44 ofmovable handle 40 such that pivoting of movable handle 40 impartslongitudinal motion to mandrel 142. Longitudinal motion of mandrel 142,in turn, translates drive sleeve 146 to pivot clamp arm 102 between theopen and clamping positions. Mandrel 142 may be fixedly coupled to drivesleeve 146 or may be coupled thereto via a force-limiting connection(not shown) to limit a clamping force applied to tissue disposed betweenclamp arm 102 and blade 124.

Activation assembly 160 includes an activation button 162 extending fromhousing 20 to enable manual manipulation by a user. In some embodiments,activation button 162 is configured as a two-mode button whereinactuation of button 162 to a first actuated position supplies energy tocompact ultrasonic transducer 80 corresponding to a “LOW” power mode,and wherein actuation of button 162 to a second actuated positionsupplies energy to compact ultrasonic transducer 80 corresponding to a“HIGH” power mode.

Wires 212, 214, 216 extending through cable 200 are configured toelectrically couple the generator (not shown) with activation button 162and first and second contacts 172, 174 for driving compact ultrasonictransducer 80 upon activation of activation button 162, e.g., in eitherthe “LOW” power mode or the “HIGH” power mode. First and second contacts172, 174 are fixed within housing 20 and configured such that first andsecond contacts 172, 174 remain electrically coupled to compactultrasonic transducer 80 regardless of the rotational orientation ofcompact ultrasonic transducer 80 relative to housing 20.

Turning now to FIGS. 3-6, compact ultrasonic transducer 80 is detailed.Compact ultrasonic transducer 80 includes a proximal casing 82, a distalhorn 84, an isolating seal 86, a piezoelectric rod array 88 including aplurality of piezoelectric rods 90, and, in embodiments, an internalcartridge 92 (FIG. 6).

Proximal casing 82 of compact ultrasonic transducer 80 includes atubular body 83 a defining a hollow interior 83 b, a solidsemi-spherical proximal cap 83 c closing the proximal end of tubularbody 83 a, and an annular flange 83 d disposed about and extendingradially outwardly from an exterior surface of tubular body 83 a.Proximal casing 82 is formed from an electrically-conductive materialand may be monolithically formed as a single piece of material, orotherwise formed such that proximal cap 83 a is sealed to the proximalend of tubular body 83 a. Annular flange 83 d enables rotatable mountingof compact ultrasonic transducer 80 within housing 20 via support 23 ofhousing 20 (see FIG. 2). Tubular body 83 a defines a generally smoothsurface in the vicinity of second contact 174 of ultrasonic surgicalinstrument 10 such that electrical communication is maintained betweentubular body 83 a and second contact 174 regardless of the rotationalorientation of compact ultrasonic transducer 80 relative to secondcontact 1740 (see FIG. 2). Threading 83 e is formed on the interiorannular surface of tubular body 83 a towards the distal end of tubularbody 83 a, the purpose of which is detailed below. In embodiments, aninternal, distally-facing surface 83 f of proximal cap 83 a defines aplurality of cylindrical-shaped indentations 83 g, each configured tosupport a proximal end of one of the piezoelectric rods 90 therein incomplementary-fit engagement therewith. In other embodiments,indentations 83 g are not provided and surface 83 f defines a planarconfiguration. In either configuration, the proximal ends ofpiezoelectric rods 90 are electrically coupled with second contact 174via the electrically-conductive proximal casing 82.

Distal horn 84 of compact ultrasonic transducer 80 is formed from anelectrically-conductive material and may be monolithically formed as asingle piece of solid material, or may otherwise be formed and/orconfigured. Distal horn 84 tapers in a proximal-to-distal direction anddefines a distal connector 85 a configured to receive proximal connector126 of waveguide 120 (FIG. 2) therein, e.g., via male-female threadedconnection, to operably couple distal horn 84 and, thus, compactultrasonic transducer 80, with waveguide 120 (FIG. 2). Distal horn 84further includes threading 85 b formed on the exterior annular surfacethereof towards the proximal end thereof, the purpose of which isdetailed below. Distal horn 84 also defines a generally smooth surfacein the vicinity of first contact 172 of ultrasonic surgical instrument10 such that electrical communication is maintained between distal horn84 and first contact 172 regardless of the rotational orientation ofcompact ultrasonic transducer 80 relative to first contact 172 (see FIG.2).

Distal horn 84 additionally defines a proximally-facing surface 85 c.Proximally-facing surface 85 c may define a plurality ofcylindrical-shaped indentations 85 d, each configured to support adistal end of one of the piezoelectric rods 90 therein incomplementary-fit engagement therewith. In other embodiments,indentations 85 d are not provided and surface 85 c defines a planarconfiguration. In either configuration, the distal ends of piezoelectricrods 90 are electrically coupled with first contact 172 via theelectrically-conductive distal horn 84.

Isolating seal 86 is formed from an electrically-insulative material anddefines a ring-shaped configuration having external threading 87 adefined on an outer annular surface thereof and internal threading 87 bdefined on an inner annular surface thereof. External threading 87 a isconfigured to engage threading 83 e of proximal casing 82 and internalthreading 87 b is configured to engage threading 85 b of distal horn 84to thereby sealingly engage proximal casing 82 and distal horn 84 withone another, thereby sealing off hollow interior 83 b of proximal casing82 while maintaining proximal casing 82 and distal horn 84 electricallyisolated from one another.

Continuing with reference to FIGS. 3-6, piezoelectric rod array 88, asnoted above, includes a plurality of piezoelectric rods 90.Piezoelectric rods 90 are arranged in a longitudinally-orienteddirection, substantially parallel (within manufacturing and materialtolerances) to a longitudinal axis of compact ultrasonic transducer 80,and may be arranged in a radially-symmetric or other suitable pattern.Although six (6) piezoelectric rods 90 (in FIGS. 4 and 5, wherein thereis no central rod) or seven (7) piezoelectric rods 90 (in FIG. 6,wherein a central rod is provided) are shown, greater or fewerpiezoelectric rods 90 are also contemplated. Piezoelectric rods 90 areconfigured for positioning within the sealed hollow interior 83 b ofproximal casing 82 with the proximal ends thereof in contact with (andthus electrically communication with) surface 83 f of proximal casing 82and the distal ends thereof in contact with (and thus electricallycommunication with) surface 85 c of distal horn 84 such thatpiezoelectric rods 90 are under compression.

In embodiments, receipt of the proximal and distal ends of piezoelectricrods 90 within indentations 83 g, 85 d, respectively, serves to maintainpiezoelectric rods 90 in position. Alternatively or additionally, asillustrated in FIG. 6, internal cartridge 92 defining a plurality ofrod-receiving receptacles 94 may be disposed within hollow interior 83 bof proximal casing 82 to maintain piezoelectric rods 90 in position.

As a result of the above-detailed configuration, compact ultrasonictransducer 80 may define a length wherein a distance between the centerof mass of piezoelectric rod array 88 and distal connector 85 a ofdistal horn 84 is one-quarter (¼) of a wavelength. Compact ultrasonictransducer 80 may alternatively define a greater such length inone-quarter (¼) wavelength intervals. The above-detailed configurationalso seals compact ultrasonic transducer 80 to enable compact ultrasonictransducer 80 to be autoclaved, cleaned, and/or otherwise sterilized forrepeated use.

In use, upon activation, one of the contacts, e.g., first contact 172,serves as the ground (neutral) electrode and the other contact, e.g.,second contact 174, serves as the alternating charged (+/−) electrode toenergize piezoelectric rods 90, thereby producing ultrasonic energy,e.g., mechanical vibration motion, that is transmitted frompiezoelectric rods 90 through distal horn 84 and waveguide 120 (FIG. 2)to blade 124 (FIG. 1) for treating tissue therewith.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

What is claimed is:
 1. A compact ultrasonic transducer for an ultrasonicsurgical instrument, the compact ultrasonic transducer comprising: aproximal casing defining a continuous outer surface and a hollowinterior, the hollow interior enclosing a plurality of indentationsarranged in a radial pattern; a plurality of piezoelectric rods, an endportion of each piezoelectric rod of the plurality of piezoelectric rodsconfigured to be inserted into one of the indentations of the pluralityof indentations such that the plurality of piezoelectric rods arearranged in a radial pattern about a longitudinal axis of a waveguide,wherein each piezoelectric rod of the plurality of piezoelectric rods isoriented along an axis parallel to the longitudinal axis; and a distalhorn including a distal connector configured to engage the waveguide,the distal horn configured to engage the proximal casing to enclose theplurality of piezoelectric rods within the hollow interior; a sealdisposed between the proximal casing and the distal horn, the sealconfigured to engage the proximal casing and the distal horn with oneanother, wherein the proximal casing and the distal horn are at leastpartially formed of an electrically-conductive material and wherein theseal is at least partially formed from an insulative material toelectrically isolate the proximal casing and the distal horn from oneanother.
 2. The compact ultrasonic transducer according to claim 1,wherein the seal is configured to sealingly engage the proximal casingand the distal horn with one another such that the hollow interior issealed closed.
 3. The compact ultrasonic transducer according to claim1, wherein one of the proximal casing or the distal horn is configuredto communicate electrical energy at a first potential to the pluralityof piezoelectric rods and wherein the other of the proximal casing orthe distal horn is configured to communicate electrical energy at asecond potential to the plurality of piezoelectric rods to energize theplurality of piezoelectric rods.
 4. The compact ultrasonic transduceraccording to claim 1, wherein the plurality of piezoelectric rodsdefines a radially-symmetric configuration relative to a longitudinalaxis defined through the compact ultrasonic transducer.
 5. The compactultrasonic transducer according to claim 1, wherein the plurality ofpiezoelectric rods is maintained in compression between a proximalsurface of the proximal casing and a distal surface of the distal horn.6. The compact ultrasonic transducer according to claim 1, wherein adistance between a center of mass of the plurality of piezoelectric rodsand the distal connector of the distal horn is one-quarter of awavelength.
 7. The compact ultrasonic transducer according to claim 1,wherein a distance between a center of mass of the plurality ofpiezoelectric rods and the distal connector of the distal horn is amultiple of one-quarter of a wavelength.
 8. The compact ultrasonictransducer according to claim 1, further comprising an internalcartridge disposed within the hollow interior and configured to retainthe plurality of piezoelectric rods therein.
 9. An ultrasonic surgicalinstrument, comprising: a housing; a waveguide extending distally fromthe housing and defining a longitudinal axis; an ultrasonic bladedisposed at a distal end of the waveguide; and a compact ultrasonictransducer supported by the housing and coupled to the waveguide suchthat ultrasonic energy produced by the compact ultrasonic transducer istransmitted along the waveguide to the ultrasonic blade for treatingtissue therewith, the compact ultrasonic transducer including: aproximal casing defining a continuous outer surface and a hollowinterior, the hollow interior enclosing a plurality of indentationsarranged in a radial pattern; a plurality of piezoelectric rods, an endportion of each piezoelectric rod of the plurality of piezoelectric rodsconfigured to be inserted into one of the indentations of the pluralityof indentations such that the plurality of piezoelectric rods arearranged in a radial pattern about a longitudinal axis of a waveguide,wherein each piezoelectric rod of the plurality of piezoelectric rods isoriented along an axis parallel to the longitudinal axis; a distal hornincluding a distal connector configured to engage the waveguide, thedistal horn configured to engage the proximal casing to enclose theplurality of piezoelectric rods within the hollow interior; a sealdisposed between the proximal casing and the distal horn, the sealconfigured to engage the proximal casing and the distal horn with oneanother, the proximal casing and the distal horn are at least partiallyformed of an electrically-conductive material and wherein the seal is atleast partially formed from an insulative material to electricallyisolate the proximal casing and the distal horn from one another. 10.The ultrasonic surgical instrument according to claim 9, wherein theseal is configured to sealingly engage the proximal casing and thedistal horn with one another such that the hollow interior is sealedclosed.
 11. The ultrasonic surgical instrument according to claim 9,further comprising first and second contacts disposed within the housingin electrical contact with the distal horn and the proximal casing,respectively, the first and second contacts configured to communicateelectrical energy at first and second potentials to the plurality ofpiezoelectric rods via the distal horn and the proximal casing,respectively, to energize the plurality of piezoelectric rods.
 12. Theultrasonic surgical instrument according to claim 11, wherein thecompact ultrasonic transducer is rotatable relative to the housing andthe first and second contacts, the first and second contacts maintainingelectrical contact with the distal horn and the proximal casing,respectively, regardless of a rotational orientation of the compactultrasonic transducer relative thereto.
 13. The ultrasonic surgicalinstrument according to claim 9, wherein the proximal casing includes anannular flange extending radially outwardly therefrom and wherein thehousing includes a support configured to receive the annular flange torotatably support the compact ultrasonic transducer at least partiallywithin the housing.
 14. The ultrasonic surgical instrument according toclaim 9, wherein the distal horn includes a distal connector configuredto engage the waveguide, and wherein a distance between a center of massof the plurality of piezoelectric rods and the distal connector isone-quarter of a wavelength.
 15. The ultrasonic surgical instrumentaccording to claim 9, further comprising a clamp arm movable relative tothe ultrasonic blade from an open position to a clamping position forclamping tissue therebetween.
 16. The ultrasonic surgical instrumentaccording to claim 15, further comprising a movable handle associatedwith the housing and operably coupled to the clamp arm such thatactuation of the movable handle moves the clamp arm from the openposition to the clamping position.